The present invention relates to a novel liquid crystalline polyester.
Recently, as to liquid crystalline polymers, researches and developments have been made actively in the field of high-performance materials utilizing high heat resistance and moldability and also in the field of functional materials utilizing changes in the liquid crystal structure caused by heat or by an external field such as electric field. On the other hand, in the functional material field, researches have been made actively for attaining the application of such polymers to optical recording, non-linear optical materials, alignment film for crystal, optical fiber and optical element for a liquid crystal display, but commercialization has not been made yet. Most of the liquid crystalline polymers being studied in the functional material field are side-chain type liquid crystalline polymers having a mesogen group capable of forming liquid crystal on a side chain, with few application examples of main-chain type liquid crystalline polymers. In the case of side-chain type liquid crystalline polymers, however, complicated steps are required in both monomer preparation and polymer preparation, and the manufacturing cost is high, so those polymers are not suitable for industrial utilization. In contrast therewith, in the case of main-chain type liquid crystalline polymers, the manufacturing process is generally short, and the polymers are superior in stability. Above all, polyesters are most suitable in all of manufacturing aspect, cost and physical properties.
On the other hand, when viewed from the application aspect, liquid crystalline polymers having optically active units in the molecule are suitable as functional materials such as optical or thermal recording materials and non-linear optical materials because they have a liquid crystal phase such as cholesteric phase or chiral smectic C phase, and studies have been made actively about those polymers. Thus, optically active liquid crystalline polyesters are novel and promising polymers for use as functional materials, but are disadvantageous in that their solubility in solvents is low. In the case of using the polymers as functional materials, they are formed into films or thin films in many cases, which are formed from solutions of the polymers. Therefore, the low solubility of the polymers has been a serious problem in practical use.
It is the object of the present invention to provide a novel polyester which is optical active, easy to prepare, less expensive to manufacture and superior in stability and in solvent-solubility.